The present invention is generally directed to a curable sealant composition and a method for manufacturing the composition. It is more specifically directed to a saturated curable sealant composition.
Polymers obtained by polymerizing or copolymerizing conjugated dienes are widely utilized for commercial purposes, such as preparation of sealant compositions. However, because these polymers have residual unsaturated double bonds in their polymer chains, the sealants are disadvantageously deficient in resistance to weather conditions, oxidation and ozone, and tend to become brittle on aging. This deficiency can be notably improved by hydrogenating such conjugated diene polymers and consequently eliminating a sufficient amount, if not all, of the unsaturated double bonds persisting in the polymer chain thereof.
Conventional hydrogenation for this purpose typically involves a three-step process. First, a polymer is formed using conjugated diene monomers and polymerization. Then, the polymer system is hydrogenated to remove double bonds in the polymer backbone. Finally, the desired functional group is placed on the ends of the polymer chain using an appropriate chemical reaction such as urethane formation, condensation, or hydrosilation. A three-step reaction, such as that described here, can often be time-consuming and expensive. Also multi-step processes are known to suffer from reduced yields over processes including fewer steps. However, the three-step process has been considered necessary in the art, because the presence of functionalities is often known to inhibit or lower the efficiency of the hydrogenation catalyst and, therefore, the hydrogenation step need to be carried out prior to functionalizing the polymers.
The present invention advantageously provides a method for preparing functionalized and hydrogenated polymer, in which the hydrogenation step is conducted in the presence of the functional group, or in other words, after the functionalization step. The process of the present invention is a less expensive and more efficient in directly preparing, e.g. alkoxysilane functionalized sealant compositions, with low amounts of remaining olefin and improved product durability.